When is stream invertebrate drift catastrophic? The role of hydraulics and sediment transport in initiating drift during flood events

AbstractThis paper explores the role of savings groups in resilience to urban climate-related disasters. Savings groups are a rapidly growing phenomenon in Africa. They are decentralized, non-institutional groups that provide millions of people excluded from the formal banking sector with a trusted, accessible, and relatively simple source of microfinance. Yet there is little work on the impacts of savings groups on resilience to disasters. In this paper, we use a combination of quantitative and qualitative evidence from Dar es Salaam (Tanzania) to shed new light on the role that savings groups play in helping households cope with climate-related shocks. Drawing on new data, we show that approximately one-quarter of households have at least one member in a group, and that these households recover from flood events faster than those who do not. We further argue that the structure of savings groups allows for considerable group oversight, reducing the high costs of monitoring and sanctioning that often undermine cooperative engagement in urban areas. This makes the savings group model a uniquely flexible form of financing that is well adapted to helping households cope with shocks such as repeated flooding. In addition to this, we posit that they may provide a foundation for community initiatives focusing on preventative action.

Download Full-text

Isolating the role of shore-parallel sediment transport in continental shelf build-up

Continental Shelf Research ◽

10.1016/j.csr.2021.104480 ◽

2021 ◽

pp. 104480

Author(s):

Uri Schattner

Keyword(s):

Sediment Transport ◽

Continental Shelf

Download Full-text

Flooding and Land Use Change in Southeast Sulawesi, Indonesia

Land ◽

10.3390/land8090139 ◽

2019 ◽

Vol 8 (9) ◽

pp. 139 ◽

Cited By ~ 1

Author(s):

Lisa C. Kelley ◽

Agung Prabowo

Keyword(s):

Land Use ◽

Land Use Change ◽

Management Practices ◽

Vegetable Production ◽

Flood Events ◽

Daily Production ◽

Extreme Flood ◽

Agrarian Societies

Flooding is a routine occurrence throughout much of the monsoonal tropics. Despite well-developed repertoires of response, agrarian societies have been ‘double exposed’ to intensifying climate change and agro-industrialization over the past several decades, often in ways that alter both the regularity of flood events and individual and community capacity for response. This paper engages these tensions by exploring everyday experiences of and responses to extreme flood events in a case study village in Southeast Sulawesi, Indonesia, which has also been the site of corporate oil palm development since 2010. We first reconstruct histories of extreme flood events along the Konawe’eha River using oral histories and satellite imagery, describing the role of these events in straining the terms of daily production and reproduction. We then outline the ways smallholder agriculturalists are responding to flood events through alterations in their land use strategies, including through the sale or leasing of flood-prone lands, the relocation of riverine vegetable production to hillside locations, and adoption of new cropping choices and management practices. We highlight the role of such responses as a driver of ongoing land use change, potentially in ways that increase systemic vulnerability to floods moving forward.

Download Full-text

Hydro-morphodynamic modelling of floodplains: the role of vegetation in suspended sediment transport

10.5194/egusphere-egu2020-22003 ◽

2020 ◽

Author(s):

Daniel A. S. Conde ◽

Robert M. Boes ◽

David F. Vetsch

Keyword(s):

Sediment Transport ◽

Suspended Sediment ◽

Flow Resistance ◽

Laboratory Data ◽

Anthropogenic Factors ◽

Future Research ◽

Suspended Sediment Transport ◽

Compound Channels ◽

Closure Models

Riverine environments are amongst the most complex ecosystems on the planet. As several anthropogenic factors have increasingly disrupted the natural dynamics of rivers, namely through stream regulation, the need for re-establishing the ecological role of these systems has gained relevance.Of particular interest are floodplains in compound channels, primarily regarded for safety against floods, but which also comprise an extensive realm for ecological functions and establishment of various species. Floodplain vegetation affects flow resistance and dispersion, playing a fundamental role in erosion and deposition of suspended sediment.The present work aims at quantifying the interaction between vegetation and suspended sediment transport on floodplains in compound channels by numerical simulations. The employed numerical tool is BASEMENT v3, a GPU-accelerated hydro-morphodynamic 2D model developed at the Laboratory of Hydraulics, Hydrology and Glaciology of ETH Zurich. In the context of the present study, the model is extended with turbulence and suspended sediment transport capabilities. The implemented closure models for turbulence pertain to three major groups, namely (i) mixing-length, (ii) production-dissipation and (iii) algebraic stress models. For suspended sediment transport, the main classical formulations from fluvial hydraulics were implemented in the numerical model.Laboratory data from flume experiments featuring suspended sediment load and vegetation-like proxies are used for model validation. The numerical results are compared with the observed water depths, velocities and sediment concentrations for different sets of experiments with varying properties, such as density and submergence. The implemented closure models for flow resistance, turbulence and suspended sediment are then combined, calibrated and classified in terms of numerical output quality.The obtained results from this modelling effort mainly contribute to understanding the applicability of 2D (depth-averaged) models to complex eco-morphodynamics scenarios. The calibration and rating of well-known closure models for turbulence and sediment transport provides relevant guidelines for both future research and practice in fluvial modelling.

Download Full-text